Electroless plating, also known as electroless deposition, is a process for depositing a layer of a conductive material, such as a metal, from a plating solution onto a substrate without the application of electrical current.
Electroless plating is commonly used in the semiconductor processing industry to deposit or “plate” a layer of a conductive metal from a plating solution onto a semiconductor wafer. Electroless plating solutions often include a reducing agent which reduces the metal in the plating solution to cause the metal to be deposited or to “plate out” over the target surface of a substrate, such as the semiconductor wafer.
Electroless plating processes involve the use of solutions or “baths” of chemicals, including, for example, metals and reducing agents. The used electroless plating solutions typically contain residual amounts of these chemicals, thereby presenting waste disposal problems. Consequently, the electroless plating waste solutions have been found to be capable of generating flammable hydrogen gas after they have been discarded. The source of hydrogen gas appears to be attributed to the reduction of water by the reducing agents in the plating solution.
Therefore, it is desirable to treat or remove the reducing agents, such as dimethylamine borane, from the electroless plating waste solutions prior to disposal of the used plating solutions.
Prior processes for removing reducing agents, such as dimethylamine borane, from an electroless semiconductor plating process either did not utilize a catalyst or did utilize a liquid acid catalyst. For processes that do not utilize a catalyst, the rate of oxidation of dimethylamine borane was extremely slow. For processes that utilize liquid acid catalysts, specialized injection and mixing equipment is required.